As part of the surveillance of the source of West Nile virus infection, adult female Culex pipience complex mosquitoes were collected in the parks and some additional areas in Yokohama City, and their subspecies were identified using the PCR method. Dry ice CDC light traps were set to collect mosquitoes in seven parks, two zoos, and a public institution in the harbor area from June to October 2009. C.p. complex was then classified into two subspecies: C.p. pallens and C.p. molestus. The ratio of C.p.m. among the female captured C.p. complex was as high as 71.8% near the Symbol Tower in the harbor area where the number of captured samples exceeded that in the other areas. In contrast, the ratio of C.p. pal. was rather higher in other areas. The results indicate that PCR-based identification is important for planning the extermination of C.p. complex, since the two subspecies breed at different water sites.

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To establish a new method for physically controlling chironomid larvae, pupae and egg mass, we delivered an ultrasonic shock under laboratory conditions and calculated the mortality. Our findings were as follows. (1) When chironomid larvae are given an ultrasonic shock at 28 kHz for more than 15 seconds, the mortality ratio is approximately 90%. (2) When chironomid larvae are given an ultrasonic shock at 45 kHz for more than 30 seconds, a mortality ratio is approximately 90%. (3) At 100 kHz, the chironomid larval mortality rate is low under almost all experiment conditions, and an ultrasonic shock almost no effect. (4) Pupae tend to exhibit a higher mortality rate than chironomid larvae at 100 kHz. (5) When the ultrasonic shock lasts 5 seconds, the mortality rate is high, similar to those at 100, 45 and 28 kHz. However, when the time is 10 seconds or more, the correlation with the mortality rate becomes high at 100<45=28 kHz; and at 30 seconds or more, the mortality rate can be expected to climb to 90% or more at either 45 or 28 kHz. (6) The egg mass mortality rate is low under almost all experiment conditions, and almost no effect can be expected.

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The temporal transition of the activity of Argentine ants was surveyed in an urban setting of Ujina, Hiroshima City, on 8 August 2007 by observation with the naked eye and digital photographs. Daytime activity of Argentine ants, which was expressed as the individual numbers in a 10cm procession, was influenced by the air temperature just above the ground surface covered with concrete. Argentine ants seemed to disappear when the air temperature exceeded 37℃ just above the ground surface.

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